Moving older subfolders in my library to an external hard drive

willthisbepublic

I want to move some old research (Subfolders in my library) to an external hard drive. What i mean is I basically want to remove the old research to free up space on my computer without losing my older research. If necessary i want to be able to take my hard drive and restore them to my zotero library when the need arises. I dont want to lose the pdf’s when moving these items to my hard drive. Is there any way I can accomplish this ?