Please check if $USER_EXPERIMENT_DIR/pretrained_lprnet_baseline18/tlt_lprnet_vtrainable_v1.0/us_lprnet_baseline18_trainable.tlt is available in your docker.
Please note that $USER_EXPERIMENT_DIR and $SPECS_DIR are the env variable inside the docker instead of the PC.
You can run following command to check if the file exists.
!tlt lprnet run ls $USER_EXPERIMENT_DIR/pretrained_lprnet_baseline18/tlt_lprnet_vtrainable_v1.0/us_lprnet_baseline18_trainable.tlt