You can't withdraw from a 401(k) while you are still employed unless it qualifies as a hardship withdrawal. You would get a 1099-R from the plan trustee and the proceeds will be subject to regular income tax, and probably a 10% penalty for early withdrawal unless you qualify for a penalty exception (you always pay the regular income tax.)
Depending on the plan agreement, in-service distributions of amounts attributable to employer contributions, after-tax contributions and any amount when over age 59½ are permitted.
I echo DoninGA's question. Qualify for what?