3881 is very new model.  Motherboard uses proprietary 6 pin ATX and 4 pin cpu connectors.  6 pinout is very likely identical to slightly older Inspiron model such as 3668. [IMAGE] 3881 You can call Dell tech support to verify whether Inspiron 3668 psu is compatible with 3881.  Give them these Dell DP/N VM8KR and 2VD0G (360w)   [IMAGE] 3668  
Recently purchased a 3881 with a 260w psu, looking to upgrade that and after looking in the manuals there is a 360w psu option but can’t seem to find it available anywhere. Any help would be appreciated 
Inspiron 3881 power supply upgrade