Je ne sais pas ce que je ferais si mon chat tombait malade.

I don’t know what I would do if my cat got sick.

It’s very simple. In this case, the would do, a conditional in English is also the conditional in French.

Otherwise, /I would like to go up to Paris for the day/ would be: J’aimerais aller à Paris pour la journée or Je voudrais aller à Paris pour la journée.

Je ferais = I would do

Je voudrais faire = I would like to do

Je ferais is when you will do something, and je voudrais faire is when you want to do something else.