Hi,

It is suggested to connect the extender to a regular wifi router. Cause the hotspot mechanism varies with different brand/manufacturers, so there may have some limits which will affect the connection/ performance of the extender. 

In other word, if there is no regular router, it is not suggested to buy an extender, while if you have bought it, you can give it a go and try to connect it to the mobile hotspot.

Good day.