One of the steps in an experiment I have to do is recrystallization from pentane-ether.

Does this mean I have to dissolve the product in a mixture of hot pentane and ether mixed together, filter , and then let the solution cool slowly to crystallize out the product?

Or does this mean I can use either pentane or ether?

Assuming I use a mixture of the two, does 50/50 mixture of the two make sense?

Easiest way to check would be to look up the solubility of your compound in each of these. I would say you only need one solvent, although there's no harm in trying the mix if you have ample product. The worst thing I can see happening is that your compound doesn't dissolve in it at all or the impurities dissolve along with it, which are both easily fixed. To do the recrystallisation itself, I would normally put a small amount of solvent in a flask containing my product and heat it to near boiling with a heat gun. It's much more efficient than pre-boiling the solvent on a hot plate. After that, if I see any precipitate persisting in the solution, I'll vacuum filter the solution through a fine, sintered funnel into an RBF. If not, then I just remove the solvent on the rot evap and dry it under high vacuum.

Do you know if the term ether would mean Ethyl ether or diethyl ether?

Yes, you will quite often find diethyl ether referred to simply as ether.