Step 1 - See if you need coordinates conversion
Select Source type - Directory.
Browse the directory where the vector file you want to import is located.
A list of vector layers will load (can be one single vector). Under "Projection" you can see either "Yes" or "No". If you see "Yes", it means that the vector you want to import matches with the location projection, and you can proceed importing it immediately. Otherwise follow the steps listed below.
Step 2 - Export CRS information from GRASS location
Very easy. In GRASS, run the command
g.proj -wef > target.prj
This will export a text file called target.prj into your home folder.
Step 3 - Reproject shapefile and import in GRASS
ogr2ogr -t_srs target.prj -s_srs vector_source.prj vector_target.shp vector_source.shp
Voila. You're done. You can now import your vector_target.shp file in the GRASS location.