tanış +dık (subordinate clause) +mız (our) + a (dative) >tanıştığımıza THE SUBORDINATE CLAUSE WITH -DİK SUFFIX IS A GRAMMAR TOPIC OF ADVANCED LEVEL. :) YOU SHOULD BE OKAY WITH THE NOUN CASES AND THE VERB TENSES BEFORE LEARNING IT. tanıştığımıza memnun oldum. (literally: I have been glad to the fact that we made acquaintance)

MEMNUN glad MEMNUN OLMAK to be glad memnun ol +du (past tense) +m >memnun oldum I have been glad .... (dative case) + memnun olmak literally: to be glad to ...

TANIMAK 1to know about someone for the first time 2to know about someone well +ş : reciprocal mood TANIŞMAK 1to make acquaintance 2to have made acquaintance in the former time

It is just two different ways of saying "nice meet you". on top of grammatical side which Mehmet already explained, I would just add, you could either go with the shorter version which is more common or the longer version which sounds more formal, to me at least.

I am glad to meet you => tanıştığımıza memnun oldum I am glad => memnun oldum