Option 1 is to leave it where it is, and it'll be handled within the new ownership company's plan.
Option 2 (which may or may not be available to you, depending on the structure of the purchase) is very simple and very common - roll over the 401(k) into an IRA. Your banking professional can do it for you. The VERY important key is for you to be sure it's a direct rollover. You CANNOT withdraw the money, and take the check and deposit it into an IRA. If you did that, you incur taxes and penalties because it was a Withdrawal.
Option 2 (which may or may not be available to you, depending on the structure of the purchase) is very simple and very common - roll over the 401(k) into an IRA. Your banking professional can do it for you. The VERY important key is for you to be sure it's a direct rollover. You CANNOT withdraw the money, and take the check and deposit it into an IRA. If you did that, you incur taxes and penalties because it was a Withdrawal.
