hi! Based on your Newfoundland example (where they hopped westward over time from Norway to Iceland to Greenland, then presumeably south via arctic islands), I'm going on the assumption that you're asking "how far from Scandinavia did the Norse explore" vs "what was their longest sailing voyage" or viking raids specifically. In which case, check out these related posts for previous responses:

• Vikings

• Vikings and Hungarians

• What is the farthest the Vikings reached in their trading and raiding expeditions?

• Two questions about the geographical reach and extent of Viking culture

• What presence did the Vikings have in the Middle East and Persia? and a blacksmithing question!