A kinematics modelling of molecular gas in the centre of NGC 3100, a FRI radio galaxy hosted by a S0 galaxy at redshift z = 0.0088. The inner region of NGC 3100 has been observed with ALMA at Band 6 during Cycle 3. The CO(2-1) 230-GHz line (rest-frequency) was clearly detected. The analysis of the line through the integrated intensity map (moment 0) and the integrated velocity map (moment 1) revealed a ring-like rotating structure. A tilted-ring model was built through the software 3D-Barolo to better understand the complex kinematics of the gas. The modelling allowed us to explore purely rotational velocity fields as well as fields including non-circular motions.