Use the hourly Erlebnisbus 2 to get to the museum. (In service from April to October)
During the high season, the Erlebnisbus 2 connects Unteruhldingen harbour, Gebhardsweiler and Meersburg harbour with an hourly service. On this route are located the popular destinations on the Bodensee Erlebniskarte (Lake Constance Experience Card) such as the Pfahlbaumuseum (stilt house museum) in Unteruhldingen, the Traktormuseum Bodensee in Gebhardsweiler, the old castle and the new palace in Meersburg.
The Erlebnisbus timetable can be found here: ErlebnisBus timetable
You can also get here by train on the Bodenseegürtelbahn (Lake Constance Belt Railway), which connects the towns of Friedrichshafen and Singen with an hourly service during the day. From Uhldingen-Mühlhofen station, you can get here conveniently with the Erlebnisbus 2 (see above), or on foot following the signs to the "Traktormuseum" (approx. 20 minutes on foot, Route on GoogleMaps). You can plan your individual travel by public transport using the Travel information of Deutschen Bahn (German Railways) or with "DB Navigator" on your smartphone.