Cuando vamos de vacaciones, siempre compramos options: 1) recuerdos 2) parques 3) estadios 4) playas

Cuando vamos de vacaciones, siempre compramos translates to "When we go on vacation, we always buy".

The options are:

Recuerdos, which is either a memento or souvenir, or a memory.
Parques, which is plural for "park".
Estadios, which means "stadiums".
Playas, which refers to beaches.

I don't think anyone is out buying parks, stadiums, or beaches every time they go on vacation, so those options are out. The most correct is recuerdos.

Cuando vamos de vacaciones, siempre compramos recuerdos.

That is correct! good job!

Me gusta nadar en la piscina which translates to i like to swim in the pool