wire to board connector for USB 3.0
As you'll find on the mechanical drawing for the part number in your image, the Molex 504187xxxx series mates with the Molex 5014186xxxx and in the 18 pin configuration that would be specifically the 504186xx's.

For example https://www.molex.co.kr/molex/products/datasheet.jsp?part=active/5041861800_CRIMP_HOUSINGS.xml

Generally we don't do sourcing questions here.  But as an illustration of the process:

1) Find the technical documentation for the side you have
2) See the listed mating family
3) Find the part number with corresponding pin count and series.

Originally I missed the matching series notation on the drawing (I expected it to be there but didn't see it) and tried to do the cross reference by family name, but these are often not sufficiently specific, and as a result I spent a couple of minutes mistakenly wading around in the 505432xxxx's, which are something a bit different even though much of the name matches.