How long does it take a message to travel from Earth to a spacecraft on Mars at its farthest from Earth about 400 million rm km?

We'll take your Word for it and use the distance of 400 million km.

The speed of radio (and light, heat, UV, X-ray, etc.) is 300,000 km/sec.

Time = (400 x 106) / (300 x 103) = 1,333 seconds = 22.2 minutes