Merging old data from old wordpress website (some webpages) to new wordpress migrated from old wordpress without losing new data in new wordpress and select specific data from old wordpress

we have hosted WordPress site called WordPress 1 on EC1 instance that have lamp on same server then we extracted all WordPress 1 and we make new instance that have lamp and WordPress migrated to new server EC2  and we keep adding data to new WordPress called WordPress 2 that include old data of WordPress 1 and additional changes after while we found that we need some webpages that we missed from old WordPress so how can we merge 2 WordPress or identify webpages data from old WordPress without overwriting WordPress 2 known that they share most of same data from before but WordPress 1 have missing data that is not reflected to WordPress 2 and WordPress 2 is current server that have changes since migrated WordPress 1 so we need build on wordpress 2 by selecting webpages (data)from wordpress so how can we identify location of those  old webpages(WordPress1) and extract it in new wordpress 2  and pointing it to the right direction without repeating common data again..