Are you on the direct TGV from Paris to Basel? That train comes into the main part of the Basel SBB station, not the outside annex where the French regional trains arrive ( track number 31). That area is a bit of a walk, but in the main station it is easy to transfer between trains.
Tomorrow, for example, the direct TGV departs Paris at 12:22 and arrives at 15:26 at Platform 5 at Basel SBB. The next train to Luzern departs from Platform 3 at 16:14. Here is a map of the station that (hopefully) shows you the plan:
https://www.sbb.ch/en/station-services/at-the-station/railway-stations/basel-sbb-station.html
From Platform 5/6, you would ascend to the pedestrian bridge and walk to the escalators down to the main hall for the ticket machines. Then just walk to Platform 3/4 which is no the same level—-left as shown on the map. Don’t go back up to the pedestrian bridge.