I need a webinar that I previously recorded and saved in my PC to be saved in the cloud

Unfortunately, since it was recorded locally to your computer, there is no easy way to upload the recording to the Zoom cloud. The only workaround is to start a new meeting, and play the recording in the meeting and record that to the cloud. 

It may just be easier to upload the recording to another cloud storage service, such as Google Drive or Dropbox, then share a link to the file from that service. 

You can see this article for some more information: https://support.zoom.us/hc/en-us/articles/202291078-Sharing-a-local-recording

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