Number of employees may be reported in a company's sustainability report, annual report and/or integrated report. The company may also report these figures directly on their website.
To find the answer, try searching in these documents for keywords such as 'employee', 'workforce' or 'personnel'. The company may report this figure in a section of their report focused on their workforce, they may also include the figure in a summary data page at the beginning of a report.
Add a comment documenting exactly where within the source you found the information (page number) and include details of any calculations you made.