[....]
Trust wallet, mycelium and electrum which of these three wallets is the most secure?
Which wallet would be better than these three wallets?
I bought Bitcoin from kucoin, so far it's in kucoin
You should not be keeping your bitcoins in an exchanger for longer than required. Well, you can even move these bitcoins to a secure location while you are still looking for good wallet. I would suggest you should create a new address from the bitcoin address generators available from various sources. I would recommend to visit GitHub bitcoin address generator which seems to be way safer.
You will get two things out of bitcoin generator. First, a private key which you should not be sharing with anyone since it is your way to access your coins over wallet where you will be importing this address.
Get your coins transferred to this newly generated address. Believe me now you are 99% secure as compared to having them on exchanger. :-)
The next up, once you select the wallet, and in this case preferably desktop version of Electrum wallet. Here you can import your above generated address and have them safely stored.