Learn Turkish: Cüzdan çekmecenin içinde. - The wallet is in the drawer.

In Turkish, saying something is 'inside' something else works like a possessive relationship. You are literally saying 'at the drawer's inside'. Because çekmece ends in a vowel, we add the genitive (possessive) suffix -nin to make it 'drawer's'.

How exactly does the word içinde (inside) break down?

It has three parts: iç means 'inside'. The -i is the possessive suffix meaning 'its' (matching the drawer). Finally, the -de is the locative suffix meaning 'in/at'. Because we are attaching -de to a third-person possessive suffix, we must insert a buffer letter -n- in between, giving us iç-i-n-de.

Could I just say Cüzdan çekmecede?

Yes, you can! Cüzdan çekmecede simply means 'The wallet is in the drawer' using the standard locative suffix -de. Using çekmecenin içinde is more specific and emphasizes that it is actually inside the physical space of the drawer, rather than just located there.

Where is the word for 'is' in this sentence?

In Turkish, there is no separate word for 'is' or 'are'. For the third person (like 'the wallet'), you do not even need to add a personal suffix to the end of the sentence. The 'is' is naturally understood from the context.