Hi M, and welcome to the forum. I'm unfamiliar with SVG files in general, but opening yours in a text editor shows that it is pretty similar to Postscript in style. The dimensions are indeed in millimeters from context (other than the width and height, which are specifically called out as mm). The page https://mpetroff.net/2013/08/analysis-of-svg-units/
has some discussion of units in SVG files.
This may be an importing bug. But please try the attached file (I don't have access to my MeshCAM PC for a while so I can't test it myself). I added "mm" suffixes to the viewBox dimensions. If that still doesn't import properly, it might be an importing bug (or at least shortcoming in dealing with this "flavor" of SVG export. In any case, it probably is something to bring up to Rob at the MeshCAM support email.
Does the program you used to generate the SVG, export as DXF possibly? DXF is much more supported in MeshCAM, probably the best support after STL files. Just a thought.