It is quite similar to LTE. In NR, there are 1008 unique PCIs using PSS and SSS as follows:
PCI = 3 x SSS + PSS
SSS: 0 to 335
PSS: 0,1,2
For example, if a 5G-NR cell has SSS value as 300 and PSS value as 1 then Physical Cell ID will be:
(3 x 300) + 1 = 900 + 1 = 901