Most tournaments require team announcements for each match to be made no later than 48 hours prior to the match, so you should be able to get this information on match day -2.
The announcement is usually made by the submission of the Match Team Sheet to the Tournament Press Officer.
You’ll need to get hold of this document and make plenty of copies so that you can circulate it to all relevant parties at the venue tomorrow.
The numbering of players, including replacements, on the Match Team Sheet is to be done according to the World Rugby Regulations regarding the numbering of players (1-15 for players starting the match and 16-22 for replacements, in order of positions with the lower numbers being front row replacements and the higher numbers being outside backs).
Below you can download a Match Team Sheet template.