Expense Reports were removed in Odoo 18.2.
See https://www.odoo.com/odoo-18-2-release-notes
Expense reports have been removed to better align with common usage, where most reports contained only a single expense. Users can still submit, approve, and post multiple expenses at once from the list view by selecting several expenses at once. For employee-paid expenses, submitting multiple expenses at once will generate a single bill per employee.

Hello,
You can find it below the Accounting -> Vendors -> Employee Expenses.
Hope it helps.