Hello!! 
Relevant forum posts... I mention that, because (as I understand it), Mr DNA substitutes the barcodes after sequencing, replacing them with what is essentially placeholder nucleotides. With all that said, you should also have received a file that identifies which barcode belongs to which sample. If you have that, you can import and demux using q2-cutadapt! Check out this tutorial for more details.
Keep us posted! :qiime2: 