"You have to remember his name!"
Translation:¡Tienes que acordarte de su nombre!
Well technically recordar and acordarse de both mean to remember. But note the two differences.
I used "tienes que acordar' and went to the dictionary (actually google translate first) to find out why I didn't use it correctly.
It appears to me that acordar is only 'to remember' when used as a reflexive form. I will have another chance at this and will update it with my attempt at a reflexive verb structure (can you use a reflexive verb with 'tengo-que'?)
took me three more tries (typos and tense errors grrrr) Tienes que acordarte de su nombre was accepted. (NOTE to self: re-learn what I thought I knew about reflexive verbs)
• Beginner’s guide to Spanish reflexive verbs