You're generally not supposed to be able to withdraw money from your 401(k) until you've reached age 59 1/2 (or 55 if you have lost or left your job). You don't indicate either your age or employment status. Both factors are critical here, and what you're using the money for can be important, too.
There are almost always staff reductions during mergers and acquisitions, so you'll need to know whether you will continue to have a job. If you are one of the downsized employees, you will be able to
1) roll your 401(k) over into an IRA that you open at a bank or online brokerage service (I prefer Ameritrade)
2) roll it over into your 401(k) plan at your new employer
3) keep it with your old employer and let them continue to pay the administration fees or
4) if you absolutely must, you can cash it out and incur the significant penalties and taxes for doing so. (Penalties are less at age 55 if you've been downsized.) I cannot emphasize how bad this option is if you are a young or middle-aged person, however.
If you maintain your job following the acquisition, you generally cannot cash out your retirement. There are rare exceptions, such as the hardship exemption that includes the purchase of a first-time home, but that's not a real good move either.
Cashing out is generally regarded as a bad idea so please consult with a financial advisor about your own individual situation. A place to start is to call the company that administers your company's 401(k), like Fidelity. They can walk you through it, but the decision needs to be yours.