In a recording of a conference call Brix says a significant number were destroyed, and then says "and we did lose a significant, I think 70 testing sites that were in urban areas". She specifies that these are mainly pharmacies.
Then Pence (?) says that he met with the Maryland family who owns 4 of the 70, which are located in DC.
These 4 pharmacies are:
Grubbs NE Capitol Hill
Grubbs NW Dupont
Grubbs SE Anacostia
Morgan’s Pharmacy Georgetown
owned by Michael and Joan Kim. These owners put out a statement 3 June 2020:
Wanted to let people know that we resumed the COVID19 testing at our Capitol Hill location today
The link also has photos of the damage.
The buildings were damaged, but not anywhere close to completely destroyed.
For more information see the Washington post article Scores of testing sites forced to close because of vandalism in civil unrest
The 70 testing sites — out of 424 in the program — that closed because of unrest are in 17 states, plus the District. They include four Rite Aids in Philadelphia and four Walgreens in Chicago.
So on the one hand, "destroyed" isn't the best term, it is more like "put out of commission", but on the other hand the 70 is just from one federal program. It shouldn't be interpreted as only 70 testing sites put out of commission.