What happen to your shares if company is sold?

Depends on how the sale is handled. If the purchaser absorbs the old company, your stock will be reissued under the new company at the new companies par value on the date of sale.

That is to say your company stock is worth $1,000 on the day of the sale, you will receive stock worth $1,000 from the new company. So the number of shares may change, not the value. Your old stock won't be worth anything.

If the buyer purchases the accounts and the equipment, but doesn't absorb the companies employees or liabilities, depending on the type of stock you hold, you may or may not receive a portion of the sale price. The stock becomes worthless.

What is generally given as "the share price" is the price for which shares were last traded. So the listed share price would simply be whatever the last person sold theirs for. However in practice heavy selling would tend to a) depress the price, since it's unlikely that there would be lots of other people wanting to buy at the same time that every single current shareholder wanted to sell, and b) trigger a suspension of trading, as a previous responder has noted.