A:Answer I own previous 7" offerings from Digiland. Aren't external card readers (Multi-readers) intended for Windows/laptop PCs/desktop PCs, and perhaps Macs? I don't believe that Android supports such readers (I tried some time ago). Android may not provide the software driver which you need. (Note which OSes support your reader device.)
Now, for a simplistic and small flashmem USB protective adapter with a fob-string, or a familiar retail USB flashmem stub (PNY, Sandisk, Lexar, etc.) it's a different story: You then need merely the simple adapter from USB to micro USB which you mention. Then, that's inserted into the micro USB jack of the tablet. Marshmallow (Android 6.0--and, everything since Android 4.0 (Icecream), along with today's Amazon Fire tablets) should then allow access to that.
