Your PC has 2 Slots and can be upgraded to 16GB (2x8GB). INSIDE YOUR DELL OPTIPLEX 3040 - (MICRO PC). Kit Capacity: 16GB.
eBay
32GB 16GB 8GB Memoria RAM DDR4 3200MHz 2666 2400 2133 MHz Laptop Memory 260Pin SODIMM PC4-19200 21300 17000 DDR4 Notebook Memory
Aliexpress UK
The only way to check this is by manually looking at your modules. However with a four slot machine like yours this is not an issue as you need to remove all of the existing ram to upgrade, but its worth knowing about.
eBay
Factory Wholesale Sodimm DDR3 4GB 8GB 2GB 1333 1600MHZ for Laptop Memoria Ram
Aliexpress UK
INSIDE YOUR DELL OPTIPLEX 5040 - MICRO TOWER. Kit Capacity: 8GB. Your PC has 4 Slots and can be upgraded to 32GB (4x8GB).
eBay
SSD 64GB 128GB 240GB 120GB 256GB 480GB 512GB 1TB 2TB 960GB Sata3 2.5 Hard Disk Disc 2.5 Internal Solid State Drive
Aliexpress UK
Your PC has 2 Slots and can be upgraded to 16GB (2x8GB). INSIDE YOUR DELL OPTIPLEX 3020 - SFF (SMALL FORM FACTOR). Kit Capacity: 16GB. 1 Year Warranty.
eBay
CORSAIR Vengeance LPX DDR3 Kit 8GB 2400MHz 2133MHz 1866MHz 1600MHz 1333MHz Desktop Memory 240Pin DIMM 1.5V DDR3 RAM
Aliexpress UK
We only supply branded memory such as Kingston, Hynix, Samsung, Micron, Crucial, Elpida, Integral etc. Please read the item specifics for more information on this product, if the title lists this as a kit, it will consist of the number of modules in the item specifics.4GB 8GB 16GB DDR3 Desktop Memory RAM Upgrade Kits - All Sizes Available.
eBay
B75 Motherboard Desktop M.2 LGA1155 For i3 i5 i7 CPU Supports DDR3 Memory SATA 3.0 USB 3.0 PEI-E VGA Interface Intel Core CPU
Aliexpress UK
Total Capacity: 64GB. INSIDE YOUR MAC PRO 2013. Your Mac Pro has 4 slots and the maximum possible upgrade is 128GB (4x32GB). Module Capacity: 16GB.
eBay
JEYI Memory RAM Heatsink With Thermal Pads, Desktop RAM Cooler DDR Radiation Dissipate for PC DIY DDR2 DDR3 DDR4 DDR5
Aliexpress UK
Condition: Opened - Never Used. Condition & Testing.
eBay
Kllisre RAM DDR4 8GB 16GB Memory 2666MHz 3200MHz Desktop Dimm High Compatible
Aliexpress UK
Then both PCBs need to be connected by 2 PINs wire (included). - Option number 2 with soldering. After this one path on JP2 jumper on your Amiga 500 motherboard need to be cut. Also one wire need to be soldered from Gary Adapter to JP2 Jumper.
eBay
Orange Pi Zero 3 4GB RAM Allwinner H618 64-Bit WiFi 5 + BT5.0 LPDDR4 16MB SPI Flash Gigabit Ethernet Android 12 TV Ubuntu 22 OS
Aliexpress UK