Deleting Backup Files from Time Machine External Hardrive

My 2.5T External Hardrive is full of backups dating back to 2019. I do not need any past a few weeks ago. I cannot move to Trash and delete, I get this message:

"The operation can’t be completed because some items had to be skipped. For each item, choose File > Get Info, make sure “Locked” is deselected, and then check the Sharing & Permissions section. When you are sure the items are unlocked and not designated as Read Only or No Access, try again."

So, I unlocked and changed permissions to Read & Write. It still returns the same message. The instructions are unclear and not user friendly. I do not want to buy another HD or completely erase it. Just delete unneeded backup files. Anyone from Apple have a solution? Make it happen, please.