Nukara Marks seem to be quite hard to acquire compared to other Reputation classes, and they are harder, but I have found a few fairly easy ways to get enough to complete your projects daily.
Hard missions on Nukara give you 15 Nukara Marks and a Tholian Equipment Requisition - Elite each. You can do two of these which should get you 30 marks.
This is short for External Hard, so it is outside. At basecamp, you can get there by selecting the Red option. It is nearby. You can often meet groups of players there.
Short for Internal Hard, the INT Hard is just inside the caves outside basecamp. There is a guy there who can give you the mission. After you have it, continue on down and go straight until you get to an elevator, select the red option.
The Vault: Ensnared.
This is good too. It takes just over 15 minutes but you can easily get 25 Nukara Marks from it.
You can also get Marks from many other STFs and missions, but these are the ones I have found most effective. Thanks for reading.
'A few deaths are a tragedy. A few million is a statistic.'