Please take a look at new batteries here:
Any of those batteries can power your tools when charged. The only issue may be if your charger is quite old it will not recognise these new lithium batteries.
If the charger has a screen to display the current battery status then it will work fine with the new batteries. If the charger only has two lights on top, red and green, then you will need a new charger as well.
This is the type of screen you should look for, the colour of the case can vary.