How to specify the directory path on external memory card?
/storage/36E2-14BB/


this is what stands for the external microSD card,

/storage/36E2-14BB/mydir


...and this is for my own custom directory on the microSD.

(I got the /storage/36E2-14BB/ from an app where the available folder options were listed in a drop-down menu. Otherwise, no clue how to arrive to the 36E2-14BB and it is is unique or universal to each microSD cards.)