The classes are float-right float-sm-right etc.
The media queries are mobile-first, so using float-sm-right would affect small screen sizes and anything wider, so there's no reason to add a class for each width. Just use the smallest screen you want to affect or float-right for all screen widths.
Official Docs:
Classes: https://getbootstrap.com/docs/4.4/utilities/float/
Updating: https://getbootstrap.com/docs/4.4/migration/#utilities
If you are updating an existing project based on an earlier version of Bootstrap, you can use sass extend to apply the rules to the old class names:
.pull-right {
@extend .float-right;
}
.pull-left {
@extend .float-left;
}