There is a tool called "create fishnet" in the Data Mangement Tools > Feature Class > Create Fishnet
You can specify the Template Extent as your 3m x 5m rectangle and then set the Cell Size Widget to 1m and Cell Size height to 2m and leave Number or Rows and Columns black. This will create a new FC with cells that are 1m by 2m.
Thank you Robert for the quick answer
interesting approach, I already tried it out but the problem is, I have more than one Polygon to fill, and they are not lined up straight...
Do you only want one 1 x 2 polygon in the 3 x 5?
If you want to completely fill the polygon you would need to change the size of your 1 x 2's as the result would not be the same area, either a 1 x 2 would be cut down or exceed the boundary. You could stack 1 x 2's 3 high but would either need to go 4 or 6 wide
If you only want to create a single 1 x 2 in the middle of the 3 x 5 that's an easy fix.
It is far easier to create the bounds and orientation at the smaller scale, then aggregate them to the larger unit, than to ensure that everything fits within those bounds. Sort of like squeezing stuff into a package... it is easier to wrap what exists than to put something into a pre-existing container.