My interfaces:
LAN1 (10.10.49.xx). Mikrotik is the Gateway of this interface PC's
LAN2 (192.168.1.xx) . This interface give me access to the internet
LAN3 (192.168.36.xx).

I want to ping and access a PC from LAN1 (10.10.49.xx) the PC's and Network devices in LAN3 Network

Any help appreciated

did you set up a masquerade rule for the LAN1 network?

Setup your IP addresses on the three interfaces as you indicate. That is all that should be needed assuming you have no firewall rules to get in the way. No NAT is needed.

No NAT is needed.

NAT is needed if devices behind LAN2, LAN3 doesn't know routes to LAN1 subnet. I.e. if the same Mikrotik device aren't default router for them.
Of course it is better to setup routes there, than to NAT it.

Thank you all for your answers.

I followed noib instructions and the problem is solved

Once again thank you all for you time