Evaluation and planning of the sites translation from php 5.4 to php 7.x

There is a functioning on the php 5.4.31 site. The site has about 70 pages with interactive elements. The site works using yii2.
It is necessary to prepare a reasoned assessment of labor (in man-hours) and an action plan for translating this site to php 7.x.
We provide the source of the site and a list of pages.
Expected result:
- recommendation to choose a specific version of php 7.x for migration
Detailed migration action plan on php 7.x (a list of tasks with job evaluation for each task)
- recommendations for developers on the best way to migrate specific pages of the site (what to pay attention to, what exactly way to solve problems).
Requirements for the degree of detail of the plan:
- The duration of each task should not exceed 16 hours (preferably no more than 8 hours)
The plan should reflect migration and subsequent verification of the operation of each page of the site.
Expectations for the artists qualifications: experience with php 5.x and php 7.x, experience of migration sites with php 5.x and php 7.x, experience with YI.
The price is negotiated.