Connect an external SSD (USB Type-C) to Mac Mini (mid 2011)?
I do not think a simple cable to going to be sufficient. The differences between Thunderbolt and USB Type-C are different enough that an adapter will be needed. One such possible adapter would be the Kanex Thunderbolt Male to USB 3.1 (G2 Type-A) Female/ eSATA Female Adapter - Black. Unfortunately, this item is more expensive than anything mentioned in your question.

Another possible way to access the speed of a SSD would be to replace your internal drive. Although, these instructions show the upgrade procedure may be difficult.