Tamasgal,   The OIDs you are looking for can be found in the MIB download found here.    Let me know if this helps.  
I am using .1.3.6.1.4.1.674.10892.5.4.700.20.1.6.1.1 for inlet temperature and .1.3.6.1.4.1.674.10892.5.4.700.20.1.6.1.2 for the exhaust temperature read-out for our R440 servers. The values I get from these sources on the new R650 machines are at least a factor 2 off, so I guess these are not the OIDs for the inlet and exhaust sensors. Where do I find the correct SNMP OIDs? I found [URL] which is a similar question but for  R620 and the link there leads to the Dell community, not to the mentioned manual. I also looked through the R650 Installation and Service Manual but no luck.
SNMP OID for inlet/exhaust temperature on R650 iDRAC9