Si no encuentro la calculadora en la mochila, le pediré una a mi tutora.

Because in Spanish, a real future condition normally uses:

• si + present indicative
• then a main clause with future, present, or an imperative

So the pattern here is:

• Si no encuentro... = if I don’t find...
• ...le pediré... = ...I’ll ask her for...

Using si + future is not standard in modern Spanish. So si no encontraré would be wrong here.

A useful model is:

• Si tengo tiempo, iré. = If I have time, I’ll go.
• Si no encuentro la calculadora, le pediré una...

Because encontrar is a stem-changing verb in the present tense.

In the present indicative, the o in the stem changes to ue in most forms:

• yo encuentro
• tú encuentras
• él/ella encuentra
• nosotros encontramos
• vosotros encontráis
• ellos encuentran

So encuentro is the correct yo form.

This change happens in the present tense, but not in forms like nosotros encontramos, and not in the future:

• encontraré = I will find

Here le means to her.

So in le pediré una a mi tutora, the le refers to mi tutora.

Spanish very often uses an indirect object pronoun even when the person is also named explicitly. This is called clitic doubling, and it is very common and natural.

So:

• Le pediré una a mi tutora. = I’ll ask my tutor for one.

Even though a mi tutora is already there, Spanish still normally keeps le.

Also, notice that le does not show gender. It can mean:

• to him
• to her
• to you (formal)

The phrase a mi tutora tells us that here it means to her.

Because pedir follows the pattern:

• pedir algo a alguien
• to ask someone for something

So in this sentence:

• una = the thing being requested
• a mi tutora = the person you are asking

That a marks the person receiving the request.

Compare:

• Pido ayuda a mi amigo. = I ask my friend for help.
• Pediré una a mi tutora. = I’ll ask my tutor for one.

Una stands in for una calculadora.

Instead of repeating the noun, Spanish can leave it out when it is already clear:

• Si no encuentro la calculadora..., le pediré una...

That una means one and agrees with the omitted noun:

• calculadora is feminine singular
• so the replacement is una, not uno

If the noun were masculine, you would use uno instead.

For example:

• No encuentro el bolígrafo. Le pediré uno.
• No encuentro la calculadora. Le pediré una.

Because calculadora is a feminine noun.

In Spanish, words that replace a noun usually agree with that noun in gender and number.

So:

• la calculadora → una
• el libro → uno

Here the omitted noun is calculadora, so the correct form is una.

Because pedir means to ask for / request, while preguntar means to ask a question.

In this sentence, the speaker wants to request an object, so pedir is the right verb.

• pedir una calculadora = to ask for a calculator
• preguntar una cosa = to ask a question / ask something

So:

• Le pediré una a mi tutora = I’ll ask my tutor for one

If you used preguntar, it would sound like you were asking a question, not requesting a calculator.

A useful contrast:

• Le pregunté la hora. = I asked her the time.
• Le pedí una calculadora. = I asked her for a calculator.

Literally, pediré means I will ask for / request.

In context, English might translate the idea as I’ll borrow one if that is clearly what the speaker means, but Spanish pedir itself does not literally mean to borrow.

If you want to make the idea of borrowing extra explicit, Spanish often says:

• pedir prestada una calculadora

Since calculadora is feminine, you get prestada.

So:

• Le pediré una a mi tutora = I’ll ask my tutor for one
• Le pediré prestada una calculadora a mi tutora = I’ll borrow a calculator from my tutor / I’ll ask my tutor to lend me a calculator

In Spain, tutor / tutora can mean a few related things depending on context.

Very often in a school context, tutora means a form tutor, homeroom teacher, or the teacher responsible for a student group.

It can also mean a tutor more generally, such as someone who guides or supports a student academically.

Here, mi tutora most likely refers to a female teacher or school tutor.

Also notice:

• tutor = male tutor
• tutora = female tutor

The given order is very natural, but Spanish word order is somewhat flexible.

This sentence is a neutral, standard order:

• Le pediré una a mi tutora.

You could also say:

• A mi tutora le pediré una.

That version puts more emphasis on a mi tutora.

What usually stays important is the structure:

• le for the indirect object
• una for the thing requested
• a mi tutora to identify the person

So the exact order can shift for emphasis, but the original version is a very natural default.

Because it is the future tense form of pedir:

• pediré = I will ask for

Spanish future forms have written accents in forms like:

• pediré
• pedirás
• pedirá
• pedirán

The accent shows the correct stress:

• pe-di-RÉ

So the stress falls on the last syllable. The accent is part of the correct spelling of the future form.