I'm sorry but at this stage I think that there is very little chance of having a live chick from that egg. It either drowned or will as soon as it tries to make the internal pip.
I had a few do that when I had too much humidity.
Being a silkie cross which are nearly always early hatch, and now overdue, without peeps or movement, i would say that it's probably a fully formed chick that suffocated in the shell instead of pipping the internal membrane.
3 options-
1 wait (not recommend)
2 toss it
3 open the middle of the...