Question

Can you please explain which of these have high resistance ?
A milliammeter or a micro ammeter ?

Answer 1

Assuming both are moving coil instruments, a microammeter has a higher resistance than a milliammeter. To achieve its very high sensititivity the number of turns on the moving coil of the microammeter must be much higher than needed for the moving coil of the milliammeter. To fit the large number of turns into the available space the wire for the coil must be of very small diameter.
These two factors, large number of turns and very small diameter wire, are responsible for the higher resistance of the microammeter.