Contacts in Outlook

I don't know why but all of my contacts have disappeared. Any Ideas !!!!!!!!!!!!!!!!!!!!!

Which Outlook: Outlook 2016 or previous, Outlook in Office 365, Outlook.com, Outlook Express? Big impact on the recommendation.

Pop mails, contacts, notes and calendars are all kept in .pst files. IMAP settings are stored in .ost file. Depending on your version and setup, these might be in different locations. If you can find your old pst you might be able to import to your current folders. When going between versions exporting and importing to a comma separated file seems to work well. When I upgraded to win10 I also bought Office 16. I have the programs on the SSD and keep my pst files and ost files on my HDD along with document, drivers, and some notes how I did it. Since my machine has an e-SATA connector, I back up the HDD monthly and store that elsewhere. Makes it easy to do a clean install and restore my machine. Remember clean SSD installs should be without any other drives or devices attached.