The "wallet ID" is specific to blockchain.com account and correspond to its login, if you have generated your address on bitaddress.org you can't have it, you should have instead the bitcoin address and it's private key.
These are the steps to import an external address from blockchain.com support:
- To import a bitcoin address from a third party platform, click on + Import Bitcoin Address and select Existing address generated outside this wallet. Enter the private key of the bitcoin address you want to import. Next, add a label for the address (optional) and select an existing sub-wallet to transfer the funds to, or leave this blank if you want the funds to remain in Imported Addresses. Click Import to complete the process.
- In the mobile app, press the three horizontal lines in the upper left corner to open the menu and select Addresses. Tap the + to the right of Imported Addresses and then scan the private key's QR code. Next, assign the address a name and press Save Name, or press No Thanks if you do not wish to give the address a name.
Anyway, if you have a bitcoin address private key you can import it on any other wallet (you have just to know in which format is).
Once you have imported the address/private key in a wallet then you can send your bitcoin to an exchange and sell them for the currency of your choice.
Here you find info on private keys format and how to import them: