It's on page 20 of the instruction manual: http://www.serviceaprilia.com/public/lu ... 202006.pdf

yes, but it's not working like that

According above mentioned manual you should turn the key to "on" and after that press the mode button for 10 seconds

Km/miles
When battery is connected, with key to
" ", hold the MODE button for more than
ten seconds to switch both the odometer
(ODO) and the tachometer from
kilometres (km) to miles (mi).
During the f i r s t f ive seconds the
instrument panel will not react with any
signal, but then current unit o f
measurement will start flashing. If MODE
button is released before ten seconds
have elapsed, the unit of measurement
will still be the one previously in use.