From the newsroom article explaining what to expect during a Mormon service:
What do people wear?
You’re welcome to wear any clothes that you feel comfortable attending a church service in. Men typically wear suits and ties, and women wear dresses or skirts. Children also usually dress up.
“We look to not only the spiritual but also the temporal, and we believe that a person who is impoverished temporally cannot blossom spiritually.” Keith McMullin - Counsellor in Presiding Bishopric
"One, two, three...let's go shopping!" Thomas S Monson - Prophet, Seer, Revelator