Unfortunately, this isn't really a trivial thing. Data in meters must be in a projection. You need
to know what the projection is, so you can de-project it into decimal degrees. The conversion
itself is simple, but without knowing the source projection (and the target datum for the degrees,
if it's different from the datum used in the projection), there's literally no way to get there.
When you have the projection, you'll also need to tell us what GIS software you have available to
do the conversion.
- V