2D sketches require certain info to define their orientation and spatial location.
If the plane that the 2D sketch is based on can be defined with the same features, then is a matter of copy and paste. Copy the sketch from one file, then select the plane in the second file and paste the sketch. Note, if there is any difference in how the plane is defined in the 2 files, the results may not be consistent.
It easier if its a 3D sketch, since those exist independent of planes, just copy and paste between the 2 files.
Specifically, select the sketch in the feature tree and then hit ctrl-C. Select a plane in the destination model, then hit ctrl-V.
3D sketches do not require a plane for destination.
All external constraints will be deleted. The sketch will retain its shape.
...additionally, if a sketch is considered common, you may want to create it as a "block", same it with a meaningful name and place it in a library for all to use.
...taking this approach one step further, maybe a "library feature" would be more appropriate?
My 2¢, ...Eddie