Hello @Nizam_thas ,
it is a surprise you still have a Cat6509 running CatOS.
There was a tool in Cisco site many years ago I think. But I am not sure it is still avaible.
First of all, you need to verify your hardware can support upgrade to native IOS I think you need sup2 and MSFC2 as a minimum and then you need to find an appropriate IOS image for that hardware.
Conversion of CatOS commands is not that difficult
in CatoS interfaces have no names but just numbers
set vlan 50 1/5
int gi1/5
switchport
switchport mode access
switchport access vlan 50
set trunk 1/5 1,2,3-10
this becomes:
int gi1/5
switchport
switchport mode trunk
switchport trunk allowed vlan 1,2,3-10
please note that in native IOS after migration you need to set each port to switchport as the default was no switcport on C6500
Also do not alter the configuration of internal trunks like 15/1 or 16/1 they need to carry all Vlans . 15/1 leads to MSFC2 on master supervisor. If there are two supervisors 2 with MSFC2 16/1 is the link to MSFC on the second supervisor.
These internal trunks are not visible after migration so you don't need to convert them just skip them.
What can be difficult to decode is that CatOS was "quite efficient" so the following command
set vlan 50 1/5,1/7-10,2/1
is actually configuring a group of ports as access ports in vlan 50
In IOS you can use interface range but you need to take care of spaces in the command to make it to be accepted.
Edit:
the conversion procedure from Hybrid mode to native IOS is reported in the document listed by BB as you can see it is quite long and HW dependent.
Hope to help
Giuseppe
