I WAS BUY LF351D BUT I DONT KNOW WHERE PIN 1 IN CHIP

[arat.1]

[arat.1]

G

[BTign.1]

One side of the top should have a steeper angle than the orther. that is the side with pins 1 ,2,3,4....

[Peter BENSCH]

@BTign.1​ if you mean the side with the bevel, then you are correct.

@arat.1​ please find the drawing in the data sheet of the LF351. In your photo, pin 1 is on the left below the ST logo:

Regards

/Peter