HI. Would like to know if arduino uno can take load of the following devices to start my project
No. It can not power a 12V motor.
Arduino Uno ports can handle 5V with a maximum of 40 mA. Take a look at the specs of your items. PIR and HC-05 can be directly connected, but motors will need external circuitry.
If No can arduino mega 2560 can handle?
What is external circutary ? can I use with motor driver ?
Show me the motor driver you want to use. Also a wiring diagram showing your power distribution.
External circuitry = circuits that are not within Arduino Uno --> a motor driver module
You should design your project before you start buying stuff.
@aarg , what makes you think that OP isn't designing ?
If I look at the specs of the two motors in your opening post, you will need at least a 10A power supply (12V).