To open its child lock, you might have its original remote control. Try these methods. Locate the manual for your television. Though slightly embarrassing, accidentally turning on the child lock to a TV is a common problem. The section In the manual about how to set the child lock feature will also explain how to unlock it.
Try a few "universal methods" for unlocking the child lock. Some televisions have a universal code built in for disabling the child lock --no matter what your code is. A common code is "0000."
Unplug your television for a few minutes. The internal battery of the TV is what helps remember what your code. If the TV is unplugged for an extended period of time, it clears the internal memory, which in turn will reset your child lock code.
If you wish to buy its original remote control, you have to contact the authorized service center. If you wish to buy a universal remote control, you should know about, which brand remote control have setup code to your TV/device brand. You should first make sure about the number of digits in the codes to your device have. There are 3-digit, 4-digit, 5-digit and even 2-digit codes. You can get this detail by the code list attached to every universal remote control. The brand name of the remote control you select isn't a matter; but, its code list should have setup codes to your TV/device brand, otherwise you can't set it up with your device.
Check this link and note which brand remote control have set-up codes
to your device brand, and buy that brand remote control, according to availability.