Moving Word for Mac Files to OneDrive

I am new to the MacBook Pro. I downloaded Microsoft's Office 365 for Mac, and then set up a OneDrive option for sharing files on my other computers. (I had used Dropbox when I was in the Windows environment.)

I copied the Word and Excel folders from Dropbox into OneDrive. This worked well for a couple of weeks. For example, when I open Excel I have a screen that shows OneDrive - Personal and On My Mac. Under OneDrive - Personal are the few folders that I placed there (including Excel and Word). Now, when I open Word, I have the same screen, but my Word folder is not shown any longer under OneDrive. I have to click-on On My Mac, and then I can retrieve them. I have no idea how this occurred. Since I want to share these files with two other computers, I need to place them back in OneDrive. Since I must have several hundred folders and files involved, I want to ensure that I do the transfer process correctly. However, when I highlight the On My Mac icon, select Word, and right-click, I don't see an option to copy the files. Obviously, there must be another procedure for accomplishing same.