They are all correct.
The prepositions "at" and "to" in these sentences mean about the same. You could use either one. However, "to" is probably used more often than "at" in these sentences.
1. I am looking for a dress to wear to the meeting.
2. I am looking for a shirt to wear to the birthday party.
3. I am looking for suits to wear to the conference.
(Are they all grammatical? Why do we have to use the preposition 'to' before a place? Can we use 'at' or 'in' instead of 'to'? What is the difference between them in meaning?)
2 answers
One could say you are wearing the shirt to the meeting and then take it off at the meeting. If you say you are wearing the shirt at the meeting there is no room for misunderstanding.
Don't ever end a sentence with "at" please! Like: where did you get the shoes at? Yuk!!!
Don't ever end a sentence with "at" please! Like: where did you get the shoes at? Yuk!!!