using switch , input binary data
and then using 74185IC , convert binary data to decimal data
and display the value on 7segment

the problem is that
i do not understand 74185IC

I understand the table



but I do not understand the circuit below
is anyone can help me please?

 

As described here, the 74185 has a built-in ROM which basically provides a look-up table to convert binary to BCD.
But I believe that is an obsolete device that is no longer generally available.