Why am I getting this error when I run my Makefile?

I am trying to run a makefile to execute my code, but it returns this error:

make: *** [makefile:8: run] Error 127

Makefile code:

main: *.o
    g++ -o main *.cpp

*.o: *.h *.cpp
    g++ -g -c *.cpp

run:
    ./main

clean:
    rm ./*.o main