None: the former Bankside power station in London houses Tate Modern, not a Guggenheim museum.
The building was originally Bankside Power Station, designed by Giles Gilbert Scott. After the power station closed, Herzog & de Meuron converted it into a museum of modern and contemporary art. Tate Modern opened in 2000 and became one of London’s major cultural attractions.
The question tests a common institutional mix-up. The Guggenheim network includes museums and collections in New York, Venice, and Bilbao, while the prominent modern-art museum at Bankside belongs to Tate, the United Kingdom’s national network of art museums.
Tate Modern’s Turbine Hall and galleries occupy the former industrial building beside the River Thames. Its location near Millennium Bridge can make it part of the same sightseeing itinerary as other London landmarks, but it is not part of the Solomon R. Guggenheim Foundation.