Try using Electromagnetic simulator to extract the RLC model of Spiral deign it easy...
Just even you can try with Sonnet Lite a free MOM based electromagnetic simulator...
This Cadence integration is not available in the free Sonnet Lite version, and the number of layers is too limited in the Lite version. You need Sonnet Professional for RFIC work.
edit: Ooops, you mean from Sonnet to Cadence? This is unusal, because that workflow does not make much sense (layout is not DRC clean, vias are not ready for manufacturing etc.) But anyway: Taking layouts from EM simulator to Cadence can be done with the GDSII file format.