How do I get from Basel to Fussen?

Yes, you can use a German rail pass, but the question is, is that the cheapest way?

The rail route to Füssen runs north to Munich and Augsburg, there is no real alternative. This will take over 6 hours. There are two routes:
Swiss route: Basel SBB - Zürich - Augsburg - Füssen
German route: Basel Badischer Bahnhof, via Germany to Augsburg - Füssen

Go to the DB website ( https://www.bahn.com/en/view/index.shtml ) and enter Basel Bad Bf to Füssen, with a date and time.
It will show advance purchase prices which are a lot cheaper than using a rail pass.

Note, when you get off your ship, Basel has two main stations: "Basel SBB" for trains to Switzerland, and "Basel Badischer Bahnhof" for trains to Germany, on opposite sides of the city centre. Make sure you go to the correct one.

Thank you Chris for clearing that up. The bahn.de website is not very clear on the use of the German Rail Pass. I think I'll still buy the pass because we are travelling for the next week to several cities in Germany. I did read a post on this forum from about 5 years ago that said a faster route from Basel to Fussen goes thru a small part of Austria; therefore I would need a point-to-point Austria pass. Do you know anything about that?

I did read a post on this forum from about 5 years ago that said a faster route from Basel to Fussen goes thru a small part of Austria; therefore I would need a point-to-point Austria pass

That's what I described as the "Swiss route": Basel SBB (CH) - Zürich (CH) - Bregenz (AT) - Lindau (DE) - Füssen (DE)
It also goes through a large part of Switzerland, then Austria and only from Lindau is it in Germany.
But it is currently quicker to use the all-German route from Basel Badischer Bahnhof, which is the one the DB site finds.

"point-to-point Austria pass" - contradiction in terms. A normal ticket is for one journey from A to B, just like you would buy for any transport. A pass is a special ticket that allows unlimited trips, within a geographical area and time limit.

If you have the time, compare advance purchase prices on the DB website with the cost of a pass. You may be able to save money that way.

Thank you, again. One last question. My daughter is traveling from Zurich to meet us in Fussen. Can she use the German Rail Pass in Zurich?

Can she use the German Rail Pass in Zurich

Only to the extent that that it covers the train from the German border to Fuessen, but she has to pay for the Swiss and Austrian portions of the trip.

You asked for faster - it's a 3.5 hour drive. If you rent a car do it just across the Rhine in Germany - way cheaper to pick up and drop off a car in the same country.