OFFTEK 8GB Replacement Memory RAM Upgrade for Dell OptiPlex 3020 (DDR3-12800 - Non-ECC) Desktop Memory at Amazon.com
Restored Dell Optiplex 3020 Tower Computer PC, 3.20 GHz Intel i5 Quad Core Gen 4, 8GB DDR3 RAM, 500GB SATA Hard Drive, Windows 10 Home 64 bit (Refurbished) - Walmart.com
4GB Memory for Dell Optiplex 3020 Micro DDR3L 1600MHz SODIMM RAM (PARTS-QUICK Brand) at Amazon.com
CMS 8GB (1X8GB) DDR3 12800 1600MHz Non ECC DIMM Memory Ram Upgrade Compatible with Dell® Optiplex 3020 Destktop - A64
How to upgrade the DELL 3020 Memory (RAM) - YouTube