i have got the answer for the error

first of all go to the website 

1) signup and subscribe to free plan 

2) after signup at the top you can see the get free api key .

3) after getting your free api key , in jupyter notebook create a variable named access_key and paste the api key inside curly braces   like this

access_key=' paste your api key here ' 

4) remember the api_key variable should be above the url variable.

5) now updated url should be as follows:

url = "http://api.exchangeratesapi.io/v1/latest?access_key={access_key}"

 with this new url and your own api key you will get the results and it has worked for me.

Thank You!