How to generate private key from blockscan address

I don’t need the priv key for my counterparty wallet,

There’s no private key for the wallet, there’s a pass phrase (also there is Easy Access key - see FAQs)

And is it possible to change my pass phrase?

No.

I need the priv key for 1FK32eU7srjwjV9HfGsNL1aaDKJXHbRDDu which is the address holding my tokens.

If the answer provided by p* is not easy to understand, check out the FAQs.