The Location in the reference should be the gallery or venue of the exhibition.
To reference a collection of works or an exhibition use the Exhibition on location guidelines.
You will need:
Format:
Artist’s name, Initials. (Year produced) Title of the work. [Type e.g. Oil on Canvas]. Location, Place. [Viewed day month year].
Example:
Fragonard, J-H. (1766) The swing. [Oil on canvas]. London, The Wallace Collection. [Viewed 24 February 2021].
In-text citation: (Fragonard, 1766)