First off, there isn't going to be any gun confiscation. The POTUS can't use executive orders to accomplish this, and any such law would never pass the Congress of the United States. Some kind of silly feel good high cap magazine ban maybe, or a ban on imported "assault rifles" but that is a LONG way from a confiscation program.
There aren't enough law enforcement officers on the payroll to start, much less finish confiscating all the guns that are out there, particularly when people start to resist or obstruct their efforts. After the first few tries, a full blown SWAT team or tactical team would have to be employed for each "raid", which would mean very few operations, like maybe two or three a day Max per department.
Like people everywhere, you'll have some cops that would go along with their orders rather than jeopardize their employment, and others that will quit rather that follow the orders. I know some of both types I believe.
I don't think we'll ever find out though, because it's just not going to come to that.