How do I get my code to work

import sqlite3
import os
import csv
# Remove database if exist
if os.path.isfile('car.db'):
    os.remove('car.db')
#Create database and open database
conn=sqlite3.connect('car.db')
db=conn.cursor()
db.execute("PRAGMA foreign_keys = ON")

db.execute("""CREATE TABLE clients
            (ClientID INTEGER PRIMARY KEY autoincrement,
            First_name TEXT,
            Surname TEXT,
            Age INTEGER,
            Address STRING,
            City TEXT,
            Postcode INTEGER,
            Email STRING,
            Phone_number INTEGER)""") 
reader = csv.reader(open('clients.txt', 'r'), delimiter=',')
for row in reader:
    to_db = [row[0], row[1], row[2], row[3], row[4], row[5], row[6], row[7], row[8] ]
    db.execute('''INSERT INTO clients
(ClientID, First_name, Surname, Age, Address, City,Postcode,Email,Phone_number)
      VALUES (?,?,?,?,?,?,?,?,?);''', to_db)
    
db.execute("""CREATE TABLE cars
            (numbID INTEGER PRIMARY KEY autoincrement,
            Make TEXT,
            Model TEXT,
            Colour TEXT,
            Year INTEGER,
            Transmission TEXT,
            Price INTEGER,
            Stock INTEGER)""")
reader = csv.reader(open('cars.txt', 'r'), delimiter=',')
for row in reader:
    to_db = [row[0], row[1], row[2], row[3], row[4], row[5], row[6], row[7] ]
    db.execute('''INSERT INTO cars
(numbID, Make, Model, Colour, Year, Transmission, Price, Stock)
      VALUES (?,?,?,?,?,?,?,?);''', to_db)

db.execute("""CREATE TABLE purchase
            (PurchaseID INTEGER PRIMARY KEY autoincrement,
            numbID INTEGER,
            ClientID INTEGER,
            Date_of_Purchase TEXT,
            ETA_of_Arrival STRING,
            FOREIGN KEY(clientID)REFERENCES clients(clientID),
            FOREIGN KEY(numbID)REFERENCES cars(numbID))""")
reader = csv.reader(open('purchase.txt', 'r'), delimiter=',')
for row in reader:
    to_db = [row[0], row[1], row[2], row[3], row[4] ]
    db.execute('''INSERT INTO purchase
(PurchaseID, ClientID, numbID, Date_of_Purchase, ETA_of_Arrival)
      VALUES (?,?,?,?,?);''', to_db)
            
conn.commit()
conn.close()

    to_db = [row[0], row[1], row[2], row[3], row[4] ]
IndexError: list index out of range