Hi,
To restore an UpdraftPlus backup into blank, new web hosting, you’d do this:
1) Install WordPress
2) Install UpdraftPlus
3) Upload your backup set
4) Press “Restore”
Since step 1) is “install WordPress”, after doing so, you then have WordPress’s wp-admin folder back, before UpdraftPlus gets involved. wp-admin is part of WordPress core, so backing it up is redundant – you can always get a fresh one from https://www.ads-software.com/download (and in fact, this is what the WordPress documentation recommends if you’ve been hacked).
If, instead, you prefer to restore your backups manually (i.e. via unzipping your files and running your SQL through phpMyAdmin), then you do this:
1) Unzip a WordPress core downloaded from www.ads-software.com/download
2) Unzip your UpdraftPlus backups
3) Run the db.gz file through phpMyAdmin
Having said that, if you really strongly want to back up WordPress core itself, then UpdraftPlus Premium can do that (https://updraftplus.com/shop/updraftplus-premium/). Also relevant: https://updraftplus.com/faqs/need-back-wordpress-core/
Best wishes,
David