Hello Arina Anikina

Yes. C57Blk6 and C57Bl/6 are the same.

C57BL/6 mouse strain is often referred to as "C57 black 6", "B6", "C57" or "black 6". C57BL/6 mice are not written as C57Blk6 mice.

The inbred mouse strain C57BL/6 has been widely used as a background strain for spontaneous and induced mutations. The C57BL/6 strain are diverged into two major groups namely, C57BL/6J and C57BL/6N, and more than 20 substrains have been established from them worldwide.

Best.