Hello. Thanks a lot for your answer.
Are you sure? At the link I posted in my first message, there’s a picture of a Seeeduino mega11 with the Sd card reader.
And I checked the pin labels on the Seeeduindo Mega11 and on the Sd card reader and they correspond: +3,3V is in the same position, the same for +5V, Gnd and D9.