There are two types of wallet in imToken: Wallet under the Identity wallet and Imported/Created wallet. Please choose the corresponding tutorial according to your own situation.
Note: Be sure to keep the mnemonic in a safe place since it represents the control over your wallet
Wallet under the Identity wallet:
Click "My Profile" -> "Manage your wallet" ->"Manage"->"Backup wallet"
Click "My Profile" -> "Manage your wallet" -> Find the wallet address -> Click "Backup wallet"