from hotel in coti area to Macau tower what is the bus number we have to take?

I think you may mean the Cotai area, right? If so, from Venetian, you can find the free shuttle bus to reach the City of Dreams, so you can easily reach the City of Dreams. Then from the City of Dreams, you can find the free shuttle bus to reach the tower.
Or as I know, from that area, you can take the local bus line 26 to reach the tower.
If you choose to take the free shuttle bus, the tickets are not needed. If you choose to take the public bus, the bus tickets can be bought on the bus.