Transformation from phidgets_high_speed_encoder to odom for SLAM

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For my master thesis with SLAM I have a robot with wheel encoders connected to a PhidgetEncoder. I want to use the phidgets_high_speed_encoder package to get the data in ROS.

My question is now how do I get the data of the encoder into the odom frame which will be used later by the SLAM algorithm. From the encoder package I get joint_states: JointState msg with position and instantaneous speed of each axis. Are there already ROS packages that convert this to odom.What else is needed to provide the odemetry data for SLAM. If there are other packages that work with the encoder used this would also help.

Thanks for your Help.

Additional information: ROS Version: ROS Foxy SLAM algorithm: SLAM Toolbox Encoder: PhidgetEncoder