Which operation could we perform in order to find the number of milliseconds in a...

The amount of milliseconds in a year must be determined.
First of all, milli means thousandth and thus one second contains 1000 milliseconds. 
${\displaystyle 1s=1000ms}$ 
Then, there are 60 seconds in one minute and thus the number of milliseconds in a minute is then obtain by multiplying the number of milliseconds in a second by the number of seconds in a minute. 
${\displaystyle 1min=60s=1000\cdot 60ms}$ 
Then, there are 60 minutes in one hour and thus the number of milliseconds in a minute by the number of milliseconds in a minute by the number of minutes in a hour. 
${\displaystyle 1h=60min=1000\cdot 60\cdot 60ms}$ 
Then, there are 24 hours in a day and thus the number of milliseconds in a day is then obtain by multiplying the number of milliseconds in an hour by the number of hours in a day. 
${\displaystyle 1day=24h=1000\cdot 60\cdot 60\cdot 24ms}$ 
Finally, we assume that there are 365 days in a year. The number of milliseconds in a year is then by multiplying the number of milliseconds in a day by the number of days in a year. 
${\displaystyle 1=year=365days=1000\cdot 60\cdot 60\cdot 24\cdot 365ms}$ 
Then mark the correct action: ${\displaystyle 1000\cdot 60\cdot 60\cdot 24\cdot 365}$