I sent tokens to the wrong network      

Start by finding out what actually happened. Open History, find the transaction, and read the network name under the amount.

The address is yours on the destination chain

This is the common case between EVM chains — Ethereum, Base, Arbitrum, Polygon and the rest share the same address format, and your recovery phrase derives the same address on all of them. The tokens are not lost. They are at your address, on a chain you were not looking at.

1. 01Switch Smartable to that network.
2. 02If the token does not appear in the list, add it by contract address from Add token.
3. 03To move it anywhere, you need a little of that chain's coin for the fee.

The address belongs to somebody else

An exchange deposit address, or a friend's. Then the funds are theirs to return. Exchanges sometimes recover deposits made on the wrong network, sometimes for a fee, and sometimes not at all — that decision is entirely theirs.

Between chains that do not share addresses

Bitcoin, Solana, Cardano and other non-EVM chains use their own address formats. A transfer to a malformed address for that chain usually fails outright rather than sending; if it went through, the coins are at whatever address the string represents on the destination chain, which is nobody's.