you should advise both make *AND* model number of your computer.
Then people here, if they do not have the answer, will research on google to see if they can find the information.
Most likely it will be on the Packard Bell website.
Once the battery has been identified, here in the UK you can generally purchase in a cheapo shop at 6 or more for £1.
If PC is a desktop, by opening the case the battery can probably be seen. Might look like a flat silver button about 1" diameter.
Good Luck - Keep us posted.