I think they may have had some 3.5 in SSDs, but it was a short lived idea.
Most cases now hold 2.5 inch drives as well as 3.5.
For cases that do not, adapters are made.
I personally like the ones that are 2 metal rails on either side
(top right in image) because they can hold 2 drives AND can be used with ANY type of case. Some of the sled style adapters do not work on some case types(mostly older cases).