The C3850-NM-2-10G is a 10Gigabit SFP+ module compatible in selected C3850 models. Cisco Part Number C3850-NM-2-10G. This module has four slots This is supported on the following switch models Two slots (left side) support only 1 G SFP modules and two slots (right side) support either 1 G SFP or 10 G SFP modules.
eBay