I want to update the form which appear after clicking on delete option below user list on All users listings.

If user has posts, it shows Attribute all content to – option for reassign other author for his posts.
It takes lots-of time to load the page, if there is thousands of users in the system.

So, I want to change the User option (Attribute all content to) from Drop-down to Type and Search.

I’ve tried to found the hooks/action but could not found that I want.

Please suggest me hooks/action for my question.

Thanks.