Error - Invalid item number

Every time I try enable, disable o remove a position which doen’t have a name I got the error: Invalid item number - although item with that number exists - when entered manually it works fine. For example:

/ip firewall src-nat print
/ip firewall src-nat disable 0

or

/ip policy-routing rule print
/ip policy-routing rule enable 2

or

/ip firewall dst-nat print
/ip firewall dst-nat remove 1

You cannot reference items by numbers in scripts.

How can I reference them then, if they do not have a name? What command should I enter instead?

Exempli gratia:

/ip firewall get [/ip firewall rule forward find comment="a comment"] address

Thanks, that’s what I needed.