I bought an ipad pro from an auction and it locked with a apple id how do I unlock it?

you likely can't

the activation lock is not really on the ipad it's a

theft protection measure on apples servers

it needs to be removed How to remove Activation Lock - Apple Support

if you don't know your appleID Recover Your Apple ID - Apple

if that does not help you then you need the assistance

of apple

Additional Support - Activation Lock (apple.com) and or

Get Support (apple.com) , Genius Bar Reservation and Apple Support Options - Apple

You don't and never will.

That iPad will always be a dead, useless device to you

No one here can help you.

Apple WILL NOT help you!

Never, EVER purchased used Apple personal mobile devices from ANY type of auction, estate/homesales, tag/lawn/garden/garage sales, antique/flea markets, car boot sales/markets, and any type of thrift stores or pawn shops.

Please properly and responsibly recycle this device.

It a a dead device that no one will ever be able to usend.

Sorry.