USDC is an ERC-20 token so you can use any ethereum wallet to store them like MEW or mycrypto wallet. Hardware wallets are the best because they are really secure but you can use a mobile wallet like Trust wallet to store them because they give us the control of our private key,.
I've never trusted mobile wallets. I'm glad that MEW made their own mobile application and now you can not use all other wallets. Only some special wallets for coins with their own blockchain