Advice please

I am fairly new to Zwift as I have completed around 1400 kms.

I am just wondering if my pace is ok for a beginner

on the flat I ride at approx 30kph wirt an RPM for around 65-68

is that an ok speed as it seems to be a good workout for me?

Yes, no, maybe.

Cadence for the most part does not have anything to do with speed within Zwift. Power is a better metric, but that can be very individual also.

Read this as far as in-game speed goes:

If your setup includes a power meter measurement then that’s the main thing that Zwift uses to determine your speed.

But the gear that your bike is in will affect how easy you find it to deliver a particular power level. That is, by spinning slow but pushing hard or by spinning fast and pushing less hard you can still achieve the same power output.

Most cyclists find pedaling at 80 to 90 rpm easier. Low cadence between 60 to 70 is usually only on steep climbs. I would recommend you try a few rides (Tempus Fugit is great for flat test ride) trying to stay at a higher cadence and see how it feels. If you can get comfortable at a higher cadence, then start trying to slowly up the average power whilst maintaining the cadence.