WMS with Barcodes for a Paper-Based Warehouse

We have a working distribution warehouse and all accounting is still done on paper. Receivers write incoming goods in notebooks, placement is done "from memory," and the picker searches for items by walking the aisles. This causes constant errors: we ship the wrong item, lose track of where inventory physically sits, and during inventory counts, the numbers don't match accounting. We need a warehouse management system (WMS) based on barcode scanning with handheld data collection terminals so every movement is recorded immediately.

The system must cover the entire operational cycle. On receiving, an employee scans the supplier's barcode (or prints our label) and verifies the quantity against the purchase order. Placement suggests a cell and records which shelf, rack, and spot the goods go to. Picking and packing are managed by the scanner: the terminal guides the route, shows the address and quantity, and doesn't let you confirm without the correct barcode. We need selective counts and full inventory by terminal with discrepancy reports and role-based access.

Integration is critical: the WMS must exchange data with the online store and accounting software in both directions so inventory, orders, and write-offs stay synchronized without manual re-entry. Please describe the proposed architecture, recommended terminals, address storage scheme, and a plan to transition from paper without stopping shipments.