qgis - How to find the proper coordinate reference system with two sets of data using different measurements or too convert one system into another

I have two different entries of data in two different spread sheets. One of the spread sheets uses a coordinate reference system that I have no idea what the units of measurement are. the properties of the shape file say the crs is +proj=longlat +datum=WGS84 +no_defs, however the data points show up off in the middle of nowhere. The other set of data is properly aligned to my map and using the same crs. Both sets of data were collected from a hand held gps which i no longer have access to. Is there some way for me to convert my data all at once to realign properly with my map? Or do I have to try using a different crs? Finally if I do use a new CRS will that not allow me to merge the layers or do types of statistical analysis?