Si no encuentro el batidor, mezclaré la salsa con un tenedor y guardaré el pelador después.

Because si no here means if ... not:

• si = if
• no = not

So Si no encuentro el batidor... means If I don’t find the whisk...

By contrast, sino is a different word meaning but rather / except in certain structures:

• No es un cuchillo, sino un tenedor. = It isn’t a knife, but rather a fork.

So in this sentence, si no must be written as two words.

In Spanish, when you talk about a real possible future condition, the usual pattern is:

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

So:

• Si no encuentro el batidor, mezclaré la salsa...
• If I don’t find the whisk, I’ll mix the sauce...

This is standard Spanish. Using si no encontraré would sound wrong here.

They describe what the speaker will do later, as a result of the condition.

• mezclaré = I will mix
• guardaré = I will put away / store

They are formed by adding future endings to the infinitive:

• mezclar
  • -é → mezclaré
• guardar
  • -é → guardaré

This is the simple future in Spanish.

Because Spanish often leaves out subject pronouns when the verb ending already makes the subject clear.

• encuentro = I find
• mezclaré = I will mix
• guardaré = I will put away

So yo is not necessary. You could say yo for emphasis or contrast, but normally it is omitted.

Because the sentence treats the whisk, sauce, and peeler as specific things, while the fork is just any fork.

• el batidor = the whisk
• la salsa = the sauce
• el pelador = the peeler
• un tenedor = a fork

Using un tenedor suggests that any fork will do. This is very natural in Spanish.

Also, Spanish uses articles more often than English, so nouns like la salsa often sound more natural than leaving the article out.

Con means with, and here it introduces the instrument used to do the action.

• mezclar la salsa con un tenedor = to mix the sauce with a fork

This is the normal way to say what tool you use in Spanish:

• cortar con un cuchillo = to cut with a knife
• escribir con un bolígrafo = to write with a pen

Because buscar and encontrar are different:

• buscar = to look for
• encontrar = to find

So:

• Si no busco el batidor... = If I don’t look for the whisk...
• Si no encuentro el batidor... = If I don’t find the whisk...

The sentence is about the result of searching, not the act of searching itself.

Not in the English sense of save money or save a file. Here guardar means something like:

• put away
• store
• put back

So guardaré el pelador después means the speaker will put the peeler away afterward.

This is a very common use of guardar with household objects.

Después means afterward / later.

In this sentence, it tells you that the action of guardar el pelador happens after the previous action or later in the sequence.

So the order is roughly:

1. if the speaker doesn’t find the whisk,
2. they will mix the sauce with a fork,
3. and afterward they will put away the peeler.

You could also see similar words like luego or después de eso in other sentences.

Yes. That would also be natural Spanish.

• Si no encuentro el batidor, voy a mezclar la salsa con un tenedor...

Both mezclaré and voy a mezclar can mean I will mix. In many everyday situations, ir a + infinitive is very common in speech. The simple future mezclaré is also correct and often feels a bit more compact or slightly more formal.

Because the sentence begins with a conditional clause:

• Si no encuentro el batidor, ...

In Spanish, when a clause like this comes first, it is normally followed by a comma before the main clause.

So this is standard punctuation:

• Si no encuentro el batidor, mezclaré la salsa...

If you reversed the order, you would usually not use that comma:

• Mezclaré la salsa con un tenedor si no encuentro el batidor.

It can be, but context matters. In Spain, people may also say batidor de varillas or simply varillas for a kitchen whisk.

So:

• batidor can be understood as a whisk or beater
• batidor de varillas is more specific
• varillas is also very common in kitchen contexts

Your sentence is understandable, but in a real kitchen conversation in Spain, you may often hear varillas too.