Okay, here's a document on NSMB cameras.

As usual, get your 4-byte numbers ready.
Read the numbers at offsets 56 (38 hex) and 60 (3C hex).
First one is the offset of camera data. Second one is the size of it! Divide it by 16 to get the amount of camera "blocks" used.
Don't forget that as with most NSMB hacking stuff, the numbers in camera data are 2-byte, little endian.

I haven't fully figured these out, yet!

Each camera block is 16 bytes long, and size is measured in pixels. (For easy conversion from pixels to tiles and back: add/remove a zero to the end in hex!)
Here is a sample block from 1-Tower:
00 03  40 09  00 01  C0 00  01 00  01 00  00 00  00 00

First, the 00 03.
This is the X position, in pixels as usual. Flip the bytes to become 0300, remove the end zero. So now we know this block is located at X position 0x30.

Next, the 40 09.
This is the Y position, as well. After conversion, we get the Y position 0x94.

Finally, the 00 01 and C0 00.
First one is width, second is height. Not too hard to figure out. I don't yet know what the other 4 numbers do. Have fun!