How to call exit function for POS Bridge with parameter of Calldata

I am working on POS Bridge for Ethereum to Matic and Matic to Ethereum NFT transfer. I have done all the steps. Transferred NFT from ethereum to matic. When I am trying to transfer nft to ethereum from matic. I burned that specific token. But i dont know how to pass calldata parameter to exit function on Root chain manager proxy contract. How to get that bytes calldata?