If it isn't charging it may be just that you need a new battery, the cord isn't working, or the charging port is damaged.
First I would try the charger cord. See if it will work to charge a different device. If it does? Then you need new cord. If it doesn't then you should try a new battery. They are pretty cheap to get.
If getting a new battery and/or new cord doesn't do it, you may have to take it into a tech and see if the tablet is salvageable, say only the port needs fixing, or if it is a brick and you need to replace it.