Do not use the existing Video folder. It can cause problems.
See #6 in Synology FAQ.
Also, make sure the user Plex has Read access to the media folder (/movies, /tv, etc). If you’re recording TV, Plex will need read/write access to the appropriate folder.
Edit: Re-read and noticed you’re moving from an existing PMS, so info below most likely redundant.
Make sure you are organizing and naming your media correctly. Note that Plex is especially picky with TV shows. Best to follow the guidelines.
Make sure you media is in a supported format. Plex does not support disc images such as ISO.
