The complete cycle route Eurovelo 10 between Rostock and Swinousje is about 400 km. If you save the section on the island Rügen for another trip then the distance is about 250 km. On the way there is e.g. a national park with virgin forest, the city Stralsund which is on the UNESCO world heritage list and several nice small cities like Greifswald and Wolgast. The trip is suitable for 3 - 8 days. Read about daily distances and accomodation options here.