You can refer "System Memory " section on page 106 of below link for details on memory configuration on R310.

https://downloads.dell.com/manuals/all-products/esuprt_ser_stor_net/esuprt_poweredge/poweredge-r310_owner%27s%20manual_en-us.pdf 

For 16GB you can use 4 no's of 4GB UDIMM/RDIMM or two 8 GB RDIMM

Part #

8GB RDIMM
FDN6D - DIMM,8GB,1066,4RX8,4WYKP, BIC
4WYKP - DIMM,8G,1066,4RX8,8,240,R,LV
3XWJ8 - DIMM,8G,1066,4RX8X72,K075P,BIC
K075P - DIMM,8G,1066,4RX8X72,8,240,REG

4GB RDIMM
7NNYD - DIMM,4G,1600,256X64,VT8FP,LGCY
7H18C - DIMM,4G,1333,2RX8X72,REG,C1KCN
XW6VT - DIMM,4G,1333,2RX8,8,240,REG,LV
9J5WF - DIMM,4G,1333,2RX8,8,240,REG,LV
C1KCN - DIMM,4G,1333,2RX8X72,8,240,REG
C59WN - DIMM,4G,1066,4RX8X72,H959F,BIC
H959F - DIMM,4G,1066,4RX8X72,8,240,REG
7H8J8 - DIMM,4G,1333,2RX8X72,C1KCN,BIC

4GB UDIMM
XKDWV - DIMM,4G,1333,2RX8,240,T192H
T192H - DIMM,4G,1333,2RX8,8,240,UBE
JV7JY - DIMM,4G,1333,2RX8,R1P74,LGCY
R1P74 - DIMM,4G,1333,2RX8,8,240,UBE,LV