You need to use the dmidecode command:
sudo dmidecode --type memory
Result is
# dmidecode 3.2
Getting SMBIOS data from sysfs.
SMBIOS 2.7 present.
Handle 0x0007, DMI type 16, 23 bytes
Physical Memory Array
Location: System Board Or Motherboard
Use: System Memory
Error Correction Type: None
Maximum Capacity: 32 GB
Error Information Handle: Not Provided
Number Of Devices: 4
Handle 0x0040, DMI type 17, 34 bytes
Memory Device
Array Handle: 0x0007
Error Information Handle: Not Provided
Total Width: 64 bits
Data Width: 64 bits
Size: 4096 MB
Form Factor: DIMM
Set: None
Locator: ChannelB-DIMM1
Bank Locator: BANK 3
Type: DDR3
Type Detail: Synchronous
Speed: 1600 MT/s
Manufacturer: Kingston
Serial Number: A3265F9A
Asset Tag: 9876543210
Part Number: 9905430-400.A00LF
Rank: 1
Configured Memory Speed: 1600 MT/s