Net stats oid of M4300-8X8F ProSAFE 8-port 10GBASE-T and 8-port 10G SFP+

All of the MIB attributes required are defined in RFC1213 MIB.

A good starting point (in bits/s) would be the ifSpeed:

.1.3.6.1.2.1.2.2.1.5
ifSpeed OBJECT-TYPE
-- FROM RFC1213-MIB, IF-MIB
SYNTAX          Gauge
MAX-ACCESS      read-only
STATUS          Mandatory
DESCRIPTION    "An estimate of the interface's current bandwidth in bits per second.  
For interfaces which do not vary in bandwidth or for those where no accurate estimation can be made, 
this object should contain the nominal bandwidth."
::= { ISO(1) org(3) DOD(6) Internet(1) mgmt(2) mib-2(1) interfaces(2) ifTable(2) ifEntry(1) 5 } 

More sophisticated math can be applied, depends based on whether the connection you measure is half-duplex or full-duplex.

Input utilization ==  ( (d)ifInOctets x 8 x 100 ) / ( (number of seconds in (d) ) x ifSpeed )

:

Output utilization == ( (d)ifOutOctets x 8 x100 ) / ( (number of seconds in (d) ) x ifSpeed )

.1.3.6.1.2.1.2.2.1.10
ifInOctets OBJECT-TYPE
-- FROM RFC1213-MIB, IF-MIB
SYNTAX          Counter
MAX-ACCESS      read-only
STATUS          Mandatory
DESCRIPTION    "The total number of octets received on the interface, including framing characters."
::= { iso(1) org(3) dod(6) internet(1) mgmt(2) mib-2(1) interfaces(2) ifTable(2) ifEntry(1) 10 } 

.1.3.6.1.2.1.2.2.1.16
ifOutOctets OBJECT-TYPE
-- FROM RFC1213-MIB, IF-MIB
SYNTAX          Counter
MAX-ACCESS      read-only
STATUS          Mandatory
DESCRIPTION    "The total number of octets transmitted out of the interface, including framing characters."
::= { ISO(1) org(3) DOD(6) Internet(1) mgmt(2) mib-2(1) interfaces(2) ifTable(2) ifEntry(1) 16 } 

Keep in mind MIB-II variables are stored as counters and it can be required take two poll cycles and figure the difference between the two.