I have starting and ending coordinates (UTM) of my lines. Also I have squares (50kmx50km) as a kmz file. I need to check which lines located in which squares. I hope, the lines are designed in such a way that they do not intersect two or more squares so maybe just ending or starting points can be used. I have 50-60 squares and more than 1000 lines. I use ArcGIS Pro and ArcMap.
Intersect the two. The result will also be a set of polylines, but review the values for a unique attribute of the original line (i.e. the original FID or ObjectID) to see if they now appear more than once (a pivot table will help here). The attributes of the squares they are in will also be copied, and you can look at a unique field there to see where the lines fall.