Hi, I'm a students and I confuse how to makea differences of using at, in, on...

please help me
Here is a summary taken from Purdue Owl ( https://owl.english.purdue.edu/owl/owlprint/594/ ):

Point in time:

On is used with days:
I will see you on Monday.
The week begins on Sunday.

At is used with noon, night, midnight, and with the time of day:
My plane leaves at noon.
The movie starts at 6 p.m.

In is used with other parts of the day, with months, with years, with seasons:
He likes to read in the afternoon.
The days are long in August.
The book was published in 1999.
The flowers will bloom in spring.

Place:

To express notions of place, English uses the following prepositions: to talk about the point itself—in; to talk about the surface—on; to talk about a general vicinity—at.
There is a wasp in the room.
I left your keys on the table.
She was waiting at the corner.

For more details, look farther down the page at the link I gave above.
Thanks for your explanation about that..
Students: Are you brave enough to let our tutors analyse your pronunciation?
I will meet you in the hotel on Monday at 12 noon.

He arrived at the airport on a mule and made the mistake of leaving the mule's plane ticket at home, in the garage, on top of the freezer.

At, on and in are prepositions and begin a prepositional phrase. To understand if the word is a preposition, place in a sentence. And if that sentence makes sense, then it's a preposition.

She flew _____ the clouds. So.... She flew (at, on, in) the clouds makes sense, or at least a grammatically correct sentence.