‘on’ is used with specific days of the week or year. –on the 1st of Jan / on Monday.
‘in’ is used with months of the year/ seasons / countries.—in April / in Summer.
From & To--is always used together to show when the action begins and when it ends. —from 1 a.m. to 3 a.m.
Of-- a preposition used to show relationships between other words, such as belonging, things made of other things
The complete sentence is--The Thane Municipal Transport (TMT) has seen a 6% drop in passenger density after the Brihanmumbai Electric Supply and Transport (BEST) reduced its bus fares recently.