Use Subscan SS58 Transform tool

You can use the following tool to convert your old Cere Mainnet wallet address to the new SS58 format.

→ https://polkadot.subscan.io/tools/ss58_transform

1. Put the old address in the Input field.
2. Select Cere in the Output Type field and hit Transform
3. OUTPUT ⇒ new address.

Use explorer.cere.network

1. Open Explorer
2. Select “Accounts”
3. Press “Transfer”
4. Insert “old format” key
5. Press on round “Avatar” icon in the left of the address to copy “new format” key

If none of those work. Try this simple address converter.