Converting dBuA to dBuV at 3m and 10m
If your "signal" is an EM wave in a vacuum or air and the H field is 1 uA/m then the E field will be that value multiplied by the impedance of free space (377 ohms or \$120\pi\$ ohms to be more precise).

So 1 uA/m maps to 377 uV/m and at those levels there is a power of 377 pW/m\$^2\$.

10 dBuA is 3.162 uA BTW.