Welcome to the forum. ![]()
You say an expansion after 10 years - are you just playing the base game? Because GD has had 2 expansions: Ashes of Malmouth in 2017 and Forgotten Gods in 2019. To be able to play the new Fangs of Asterkarn when it releases you’ll need the base game and both those expansions as well.
And if you want to switch to local saves follow the instructions in this thread.
Then just back your saves up regularly to an external drive like a USB key and then you can put them on another PC if you want to.