Once you enter the station, the compass to the left of your scanner, that you used to supercruise to the station will point to your landing pad. Before you enter the station it points to the station entrance. Just like when navigating to the station, if the dot on the compass is an outline the pad is behind you. Get that dot solid and in the middle of the compass and you'll be pointed straight at your assigned pad.
Additionally, above your scanner there is a notification about which landing pad you've been assigned, and the landing pads have the number floating over them.
With a station, the pad and number will always be oriented so that the number is easy to see as you enter the station. However, there's a few pads very near the entrance that you can't really see and instead have to stop quickly and reorient right as you enter the station.
With an outpost the compass will point to the landing pad as soon as you are given docking clearance. These can be a bit trickier because you can approach an outpost from an angle where you can't read the number or maybe even can't see your assigned pad at all. If you target the station and rotate around a bit, the station diagram in your target scanning (left of main scanner) will rotate to match, and you can often see a certain type of "block" that has the landing pad on each side and aim for the opposite side. Correlating that with what your compass and cockpit view tell you can usually guide you to the right pad. If you can't figure it out from that, often the easiest thing is just to go slightly past the station until the dot is at the edge of the compass, then stop and flip around and take another look.