I don’t have my old Mac. How can I upload my information

Did you have iCloud Photos, iCloud Drive, iCloud Contacts, etc turned on in your old Mac when you had it? If not sure, use any internet browser and log into www.icloud.com

If you see data there (e.g., Photos, contacts, etc), when you turn on the options in your new Mac (using the same Apple ID for iCloud as the old Mac) at Apple menu > System Preferences > Apple ID > iCloud (in the preferences sidebar) > Photos, iCloud Drive, Calendars, Notes, etc., the data will sync to your new Mac.

Also see: Set up and use iCloud Photos - Apple Support

and

Set up iCloud Drive - Apple Support

and

Set up and use iCloud Contacts - Apple Support