Is there a possibility to convert .vsdx files to .vsd format.
Converting newer Microsoft Visio Drawings directly to older Microsoft Visio Drawings (.vsdx to .vsd conversion) might be quite challenging, since the older .vsd format is no longer supported in the latest Microsoft Visio versions. This makes such a conversion very difficult, unless you own an older MS Visio version (which still works with .vsd format).
Should you have access to MS Visio 2010 version, you will need to download the MS Visio Compatibility Pack from the Microsoft website. This pack extends the program's functions by adding support of the .vsdx format.
Unfortunately, macOS users will have to search for alternatives, such as ConceptDraw Pro, a diagramming software (available for both Windows and macOS users).
A diagramming program for Apple Mac and Windows
A vector based diagramming software from Microsoft