convert string column into numeric in Python

df_auto['Kilometers'] = df_auto['Kilometers'].str.extract('(\d+\.?\d*)', expand=False).astype(int)

#########################################################
df_jobs['Salary to'] = df_jobs['Salary'].str.findall(r'([-+]?\d*\.\d+|\d+)').str[-1]
df_jobs['Salary from'] = df_jobs['Salary from'].astype(float)


###########################################################

df_auto['Kilometers_test'] = df_auto['Kilometers'].str.extract('(\d+\ \d*)', expand=False) # 40 000
df_auto['Kilometers_test'] = pd.to_numeric(df_auto['Kilometers_test'].str.replace(" ", ""), errors = 'coerce')