Incorrect syntax near the keyword WHERE

why am i getting this error , below is the code
insertuserhistory = new SqlCommand("insert into tbl_usershistory (userid,FirstName,LastName,Code,Description,Trial,Expired,TrialActivatedBy,DateofPurchase,EndofPurchase) VALUES(N'"+Label1.Text+"',N'"+Labelfirstnsme.Text+"',N'"+Labellastname.Text+"',N'"+Label4.Text+"',N'"+LabelDescription.Text+"',N'"+triallabel.Text+"',N'"+expiredTrial+"',N'"+Labeltrialactivatedby.Text+"',N'"+TxtTrialStart.Text+"',N'"+expiration+"') WHERE userid='" + Label1.Text + "' AND Code='" + Label4.Text + "' AND Expired='True'", conn);